In equipment or presses for printing articles such as a continuous supply of tickets, tags and labels, for example, as disclosed in U.S. Pat. No. 3,742,851 which issued to the assignee of the present invention, it has been found highly desirable to provide for precisely controlling the application of ink to the face of the printing plate mounted on the print cylinder so that precision lines or art work may be printed on the articles. For example, in recent years, a system has been developed for optically reading coded information printed on labels adapted to be attached to various products. Preferably, the machine readable coded information consists of a series of closely spaced parallel bars some of which are wide and the others of which are narrow. These bars must be precisely printed at a high speed, requiring a precise control over the amount of ink which is applied to the raised printing face of the printing plate. It is also important to supply the ink applying roll with a continuous supply of ink and to provide for recirculating the overflow or excess ink to the ink supply reservoir or container.
Various systems and mechanisms have been proposed or used for adjusting the position of an ink applying roll relative to a print cylinder which carries a printing plate. For example, U.S. Pat. No. 2,703,525 and No. 3,645,202 disclose two different types of such mechanisms. Furthermore, various systems and mechanisms have been proposed or used for supplying ink to the ink applying roll of a printing press and for returning excess or overflow ink to the ink supply reservoir or container. For example, U.S. Pat. No. 2,253,122, No. 2,869,460 and above patent No. 3,742,851 disclose different types of ink recirculating systems. cl SUMMARY OF THE INVENTION
The present invention is directed to an improved system for applying ink to the face of a printing plate on a printing machine and which provides, as one important feature, an improved means for precisely controlling the amount of ink which is applied to the printing plate. In addition, the present invention provides an improved system for recirculating ink to the ink applying means. In accordance with the illustrated embodiments of the invention, the ink applying system incorporates a lower ink distributing roll which is positioned adjacent an upper ink applying roll in horizontally offset relation to define a nip zone for receiving a supply of ink. The rolls are driven in timed relation by a set of gears positioned at corresponding ends of the rolls, and the rolls are supported as a unit for precision adjustment at opposite ends relative to the print cylinder. The lower ink distributing roll is also adjustable relative to the ink applying roll to control precisely the film of ink carried by the ink applying roll to the face of the printing plate.
The ink distributing and applying rolls are positioned within a substantially enclosed ink fountain housing which receives a supply of ink from a recirculating reciprocating plunger-type pump system actuated by the same drive motor which rotates the print cylinder and the ink distributing and applying rolls. In the illustrated embodiments, the recirculating pump system includes a manifold and cap assembly which is adapted to receive a molded plastic ink bottle or container and which also supports a set of concentric ink supply and return tubes depending into the container. The lower end portions of the tubes support a set of corresponding concentrically disposed molded plastic check valve bodies which snap-fit onto the tubes.
In addition to the precision control of the application of the ink of the printing plate, the construction of the ink supplying and applying system provides for dependable service during high speed operation of the printing press. Furthermore, other features and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.